Stoker control system



Sept H, 1951 H. G. MANSON ET AL STOKER CONTROL SYSTEM 4 Sheets-Sheet 1 Original Filed May 10, 1948 W WM m M ATTORNEYS Sept. 11, 1951 H. G. MANSON ET AL 5 54 STOKER CONTROL SYSTEM Original Filed May 10, 1948 4 Sheets-Sheet 2 HAP/P) 6. AIM $0M Pose-Er 7 HANSEN 19 77' 0 P/VE KS Sept. 11, 1951 H. G. MANSON ETAL STOKER CONTROL SYSTEM 4 Shees-Shset 3 208527 7? HANSEN Original Filed May 1Q, 1948 ATTOF/VE Y5 Sept. 11, 1951 H. G. MANSON ETAL STOKER CONTROL SYSTEM 4 Sheets-Sheet 4 Original Filed m 10, 1948 1/ l/l/ lI/l/ll/ THERIWOSTAT lNl/fNTOES P085187 P HANSEN if TI'OPA/E Y8 Patented Sept. 11, 1951 STOKER CONTROL. SYSTEM Harry G; Manson and Robert P'. Hansen, Prince..-

ton, Ind., assignors to Hansen: Manufacturing;

diana Company, Princeton, Indl, .a'zcorporation of- In- Original application May 10, 1948,. Serial No. 26;058. Divided and thisappli'cat'i'on March-25, 1949, 'Seria'lNo'. 83,418

9 Claims. 1

This invention relates to control switches, and

particularly to devices of this type especially adapted: for. use in controllingstokers and. similar mechanisms. This application. is a division of applicationof Harry G. Manson and. RobertP. Hansen, Serial No. 26,058, filed May 10, 1948, resulting in U. S. LettersPatentNo.2,542,824; dated February 20, 1951..

Most. automatic Stoker-controls include an overallcontrolling portionwhich selects between.normaldaytime Stoker operation, and nighttime. operation whichv is generally of a reducedrfire nature.

suchtcontrols also. usually include, and ordinarily as. an entirely separate mechanism, instrumentalities for effecting. reduceddire opera tion of the Stoker. during thenight period.

, Areduced-firecontrol of this typeconsists of means for intermittently energizing the stoker drive motor. sothat the fire which the stoker is feeding is maintained at some predetermined burning rate :WhiCh prevents the fire. from going out during the night and which may also, especially in severe. weather; provide suiiicient heat units-to; maintain thelbuilding being heatedat a certain temperature.

} As. mentioned. before, stoker controls of this type-generally, includethe two sections identified above and which. are. generally separately constructeclralthough often placed in asingle frame to, be sold as a unit.

The present, invention has. as its primary obj ec t the construction of a stoker control arrange- ;Inentvwhichis truly unitary incharacter. in that it employs only a, single driving motor.

Another object of this invention is to provide an improved. stoker control which is very convenient toadjustat any time.

It is alsoanobject of this inventionto provide .astokercontrol including atime switch having, a. drivernpart which is-engaged. and disengaged from .thedrivingmotorin order to make. it selectively effective or inefiective.

Astill further object. is the provision of a .stoker control device which is connected with building thermostats and the like and which operates over a24=hour period to control a stoker. through-normal and reduced-firing operations.

These. andother objects and advantages will becomemore apparent upon reference to thefollowingdescription. taken in connectionw-ith the accompanying drawings in which:

. Figure 1. isa front elevational viewv showing a control switch constructed according to this. in:- v ntion';

Figure 2 is a: viewlooking at. the switch: in. the same direction as Figure" L but-- with the: front cover of the switch removed in order to show "the various gear trains;and1other-devices23 Figure? 3cis--a-. verticai'sectlon indicated. by the lines: 3:-3: cnFigures 1: and: 2:.

Figure 4' is a"- verticalrsecti'onindicatedby the lines 4'--4-' oiri Figures I; and; 2t;

Figure 5 is a; plan"- section indicated; by" the 1ines"5'5-on Figures l= and 2.

Figure 6 is aplan section: indicated by the lines 6-5" on Figures-1 hand? 2;

Figure '7' is' a sectional viewdndicated' the lines 1-4 on Figures 5 and 6; 1

Figure 8 is averticalsection indiczalted by' the finest-8cm Figures land 2; and" Figure 9 is a wiring diagram-showinghow the switch of this invention could be connectedin circuit with a StOkSYHlOtOF and suitable th'ermo static switches for'controlli'ng the' operation of a stoker. Referringto the drawings, thedevice of this invention comprises a frame' or"boxlik'e*' enclosure H3, and formed thereon, as at f2", is a dial inscribed with numerals for indicating. th'ehour and whether it be a. m. or p. m: Apointer' I 4 sweeps over the said dial and an adjustin'giknob !6- may be provided for correcting the position-I oi the pointer M shouldthe: indicating? position thereof be incorrect.

Adjacent the stationary dial 1 2" is: a p'air' of other similarlyi'ns'cribed dials l8 and- '20;- said dials being rotatable". and gearedltothe pointer M to rotate inunison therewith. Associated with-each of the di8;1S -|8'aIId-'2U is: a: pointer-1'22 adj ustably connected therewith "and adapted. for normally rotating" with: the said. dialsc These pointers are adjustable to indicate" certain: times of the: day at which the device effects controlling adjustments in the stoker motor opera-ting: circui-ts:

Alsomounted on the--frame HHS-a reduced-fire or cycling arrangement Z -Q including. a dial; 26 over which is movable a pointer. 28.. Thedevice 24, as will become apparent hereinaften isthe'reduced-firepa-rt of thestoken controlandds-operable for: intermittently energizing the stoker:

'drive motor and for predetermined. periods of time thereby to maintain the fed fire-atareduced rateduring the nightor during-any other period that. the. building. being. warmed would; nothave to'bekept up. to full. temperature.

The drive arrangementior the pointer; and the dials l8 andazn isbestillustratedinr Figures and. In these figures. .it'iwilll'be ;seen.that" the frame. l6. mounts. a synchronous. electric-.drive.

motor 38 which carries a pinion 32. The pinion 32 runs on a gear 34 which is mounted on a shaft with another pinion 3B. The pinion 38 in turn drives through a gear 38 which is mounted on the same shaft as the pinion 40. The pinion 40 drives into a gear 42 which is frictionally connected with the shaft 44 that supports the ad justing knob I6 referred to above.

Pinned to the shaft 44 is another drive gear 48 and meshing with the gear 48. is a gear 48 carried on the shaft 50 which drives the pointer I4. Also meshing with the gear 4B'is a gear 52 which is the same size as the gear 48 and which is connected with the dial 20. A gear 54 of the same size as the gears 48 and 52 with the gear 46 and is connected for driving the dial I8. The connections between the gears 52 and 54 and their respective dials I8 and 20 is best illustrated in Figure 6 wherein it will be seen thate'ach of the said-gears has on the end of which is mounted the associated dial; I

The frictional connection of the gear 42 with the shaft 44 permits the simultaneous adjustment of the pointer? tandthe dials I8 and 20 in order'to correct for the'position thereof when the clock has been stopped due to the power being shutoff orfor some other reason. Normally, the frictional connection between the the shaft 44 is effected by the spring washer in dicated at 43 and isv sufficient for maintaining a driving connection between the said gear and shaft. i

also meshes a sleeve part and gear 42 and Eachjof -the;pointers 22" is connected with its 4 corresponding jdial -I8 or 20 by means of a spring pressedi clutch portion indicated at 56. The pointers are squared to .-fit over the square portions 58 of theshafts 60 and there is thus normally'efiected a driving engagement between the shafts and the dials. However, when the pointers are adjustedrelative to the dials by pulling the .pointers out against their loading springs and turning them, .--the said shafts rotate with thepointers while the dials remain stationary. Attached to the shafts 60, thatare within the recess 62 formed-in the back wall of the frame I0, are apair of cam wheels 64 each of which carries a cam member 68 adapted for engagement with a snap action switch mechanism indicated at 68. I

This switch mechanism will be best seen in Figures Band '7; and it will be apparent that it comprises a toggle mechanism including an arm having a roller I0 at the end thereof which will be in a leftward position after -the switch has'been actuated by'the cam 86 associated with the dial I8, and'in a rightward position after the switch has been actuatedby the cam 86 associated with the dial 20. The s'witch'proper, associated with the toggle switch arrangement, includes a movable contact I2 which closes on a stationary contact I4 when the roller'is in its leftward position, and which closes on a contact I6 when the roller is in its rightward position.

As explained above, each of the cam wheels 84 can be adjusted relative to its driving disc and therebyaccurately controls the time of day when the switch mechanism 08 willbe actuated by the cams carried by the said cam wheels. Thus, over a period of 24 hours, the switch mechanism at 68 will first be actuated into one position by one of the cam wheels and then into another position by the other of thecam wheels. f V .The aforementionedswitch arrangement is for the purpose, of selecting between daytime and nighttime operation of the stokerQ During the daytime, as will be seen hereinafter, the control of the stoker is effected by a thermostatic switch located in the building being heated. During nighttime operation, the operation of the stoker is controlled by a reduced-fire mechanism which intermittently energizes the stoker motor for predetermined periods of time.

The reduced-fire portion of the stoker control of this invention is best seen in Figures 2 and 4. This part of the stoker control comprises a frame or bracket 18 which is mounted for free swinging movement about a shaft extending through the back wall of the frame or housing I0.

Mounted in the bracket I8 is a gear train com= .3 prising a gear 82 pinned to the shaft 80, a inion 84 meshing with the gear 82 and a gear 86 rigid- 1y mounted with the pinion 84. The shaft 80 also has mounted thereon an arm 88 and positioned in the rotative path of the arm 88 is a pair of spaced stops 90 and 92 carried by the bracket I8.

The stop 90 is angularly adjustable relative to the bracket I8 by means of a knob 94 which is rigidly connected with the stop 80 and which may provide, support for the inner end of the shaft 80 as at 98.

A spring washer 98 provides frictional engagement between the stop member 90 and the bracket I8 so that when the said stop member is positioned by-turning the knob 84, it will thereafter remain in that position relative to the bracket I8 until again moved by the said knob.

Reference to Figure 2 will reveal that extending downwardly from the bottom of the bracket I8 is a rod I00 which extends through a slot I02 in a plate I04 pivoted on a screw, I08, see Fig. 4. A spring I08 bears between the plate I04 and the bottom of the bracket 18 and provides for a toggle action of the bracket as it moves about the shaft 80, thus snapping it sharply into its two operative positions.

The extreme positions to which the bracket I8 will move are determined by the slot I02 in late I04 and the stops I I0 positioned one on each side of plate I04 and predetermining the limits of movement thereof.

When the bracket I8 is in its full line Figure 2 1 position, the gear 86 meshes with an idler pinion II2 mounted on the back of the housing I0 and which is adapted for being driven through a gear train including the gears II4, I I8, II 8 and pinion I20 by the gear 38. When the bracket I8 is in its other operative position, as shown in dotdash outline in Figure 2, the gear 88 is spaced 1forum the pinion I I2 and is thus not driven there- Movement of the bracket I8 into its full line Figure 2 position is accomplished by a torsion spring I22 connected between the shaft 80 and the back wall of the housing I 0. This spring acts through the shaft 80 and arm 88 against stop 00 and rotates the bracket 18 counterclockwise. Thereafter, the bracket I8 is moved into its other position by the engagement of the arm 88 with the stop 92.

The driving of the gear train in the bracket I8 exerts a thrust on the stop 90 which snaps the bracket into its dot-dash position in Figure 2. It will be noted that at that time the spring I 22 is operative to drive the gear train and the arm 88 back to their starting positions, thus to bring about movement of the bracket I8 back to its full line Figure 2 position and reengagement of the gear 88 and pinion I I2.

Mounted about the shaft 80 is a cam plate I24 lies/trig a pin I26 therein which: isuadapted' fon engaging the bifurcated end I28 of onearm of the toggle actionswitch:I 303 'It' will be apparent: that clockwise "movement clbckwise movement 1 of" the. said cam plate will.

open the'said contacts. The cam plate-isretained in frictional driving engagementwith the shaft 81) liymeansof the disc :I 3 and 'therspring washer I38"; The'cam plate-is further adjustable-relative to: thersaidi disc by means of the screw and slot arrangement I38:

The operation. of" the reducecl fire; portion of: thestoker 'control'is: as follows Assuming the braekeltzlil to. be. moved to" its- Ei'gure: 2': positiomhthe. gear 85: will; be driven" through'i the: pinion: Iii-2. anti. gear 82;, driven: by; pinionsBfl: will-.drive'the-shaft 8.8; thereby driving the disc- I'34:and;cam;p1ai-e:: IZ I in a;clockwiset'di.- reaction;

Afterfaxxpredeterminedz time-,theepin I 26: carriedz by." the: cam; plate will engage and. trip the. toggle: switch." I38 into?- closed positioni Thereaftersthe: said: switch" will remain: closed; during. continuous clockwise movement cit the camplate; Rotationof the: cam plate; and gearing in the bracket. "!'-8:Wi11': continue until the arm 88- enages-:the stop-92. At that time th bracket I3 will: bevsnappedpinto its dot-dash Figure 2 position;

The: spring; Iiizrnow'. drives the gearing in the bracket 18;. the cam :platesand .the a1'm--.83,back'- warerly; and during this retracting movement of thercam=p1ate-the-switch I 3B- will again be trippedinto: its.--op;en-= position. When the arm. t'ilihas moved-to the pointwwhere-it engages the stop 96, it: will. again shift the bracket 18 intoits- Figum 2- position,- and a i new cyclewill commence.

It; will: be: apparent: that; the. length of. time that-. the switch 351-is-clesed -Wil1 -be-determined bygtwthe location of the cam; plate. I 24 relative to: the disc I34- a-notthatthes. overall. period; including both the closedand open periods; for. thevswitclr Isa-will be determined by-thespacingpf the-stopsflll and 921';

- During; normal daytime operation of. the Stoker itiis; not. desired" :to use the reducedefire *feature; and-.to.-this end, the bracket"IQ l-has-aarod ME].

projecting. therefrom. which. is adapted. for, en-

gagement with the plunger I 6-2 of a solenoid; I44; Energization' of; the-solenoid M4 will move. the plunger. 42s rightwardly and thrust the: bracket IMin a; directi0n to hold: the bracket-J-8-.- in its dotedash Figure 2-..position:

The switches and the solenoid :referredto above are connected in circuit with a stoker motor. as show-nin Figure 9; In-Figure 9 the timingamotor 3i): iswccnnected between the power lines L I and L'Z-rand in: series with an on-off: selector switch Hi6:- The power line LI is also connectedlby a wire- Il8 with the movable contact 1-2 of the switching device?- 68: The contact I6 oithis switching-device is connected by a wire I50 with one side ofa'normally open thermostatic switch I5'2; .the other side of which is connected by.-a Wire I514 with one terminal'of the solenoid; I44;

Th otherisid'e of the solenoid I45 is connected by'a Wire I55 with the power-1ine-L2: The-other contact I l-of, the switchingdevice 5-8 is connected byra wire I58 with the wire I54 anclal-so hy a wire I fifiwith one side of the-thermostatic switch-I62 the other side of which is connected by a: wire lfifliwith one side of axrelay coil I66.

The. other? side of: the relay coil. I665, is; con.-

erable; when: energized, to morezitsblade I68?" into position tocomplete' a: circuit; bBtWQGI'lithfi? lines LI and L2, andn through the; stokerg-motor" indicatediati H02. Thezend ofjthecoil; I66 cone nected" with the. wire. IB L is also connected by" anwire= It12zwith one=ofzthe contacts I312; thesother of: which; is connectedlby aiz wire I14 withwthea powersline'aLIJ.

The thermostatic:switch: I252? referredrtorabove'r is normally open-below apredetermined temperature': and: closed. above the: said temperature; whereassthe thermostatic". switch I6 2 is-"norma-lly closed below a: predetermined: temperature and.

opens: above; that? temperature: The: switclr I62; is for the purpose of effecting normalfdaytime; controltofthestoker 'motonrelaymoi-lf I 5 6; whereas the switch I52" becomes: effective:- for nighttime. operation. and; controls"; the; efiectiveness-s of the? cycling reducedsfire;arrangement-which includes, theito'ggle switch- I'3II'5.

Operation Theoperationof-the stokercontrol unit of this invention is briefly' as follows:

The stoker; motor is connected incircuit with the control unit; the 'stoker -motor control relay; and the-control thermostats as=shown inFi'gure 9.

It will be" understood that other" suitable. and well known" thermostatic control elements could be added to the-circuit as itis'desired, as; forex ample, a stackcontrol toprevent the fi're' 'b'ed from overheating; or other elements designedto detect certain- 4 tem peratures and translate them into control impulses:

The'unit'having been=connectedin 'circuit with the stoker motor and thecontrolling thermostats, the-pointers 2'2 are set relative to their respective dials I8 and 20 to select the times at whichn'ormal daytime'operationsof the-Stoker motor begin and 'endf The-"beginning of the time operation will" be determined by the sett'ing ofth'e' pointer 22 asso=- ciated with the dial" I 8? and this pointer and dial" arrangement is operativeL-t'o throw: the switch mechanism at 68 into the position.- shown: in l i'gune 9i" wherein the 5 contact; member 12:? closes on. thencontactv 14:

At: this time the thermostatic switch I622 is connected in "series" with the relaycoil I66; and a circuit is also completed" through the solenoid actuator: I44 which: throws: the reduced fire cycling control: out of .engagementzwith the drive motor: Under these conditions; the -relaycoil I SEE is-v energized or etc-energized: as determined by the thermostatic switch I62.

When the temperature =of' the? building" being heated bythe Stoker: controlled furnace reaches a: predetermined temperature; the switch I62; opens and'the relay coil lfifiiiis'de-energized.and; in turn; cle-energizes"thestoker'motor I10; A's-- mentioned b'efore, thecontro'l circuit for 'therelay coil I66 can includestaclr controls low water controls, and other control devices that are well known i'na theart; if desired;

the end of" a normal daytime operating cycle the switch mechanism 68'is engaged:by:the cam associated with the dial andrpointer'zfl; .22.; and tis shiftert into: position to a close the contact member:- 1'2: on the contact- I6; At' thisrtime the-thermostatic switch IE2 is -cut-out :offthercir.e cuitiand? loses its; control :over therelay; coil I663 Theacircuittthrouglrz the solenoid: actuatcn- I H is 'aisointerrupted; ancrits control.overthereducedfirezcycl'inggcontrolris5alsor1ost..

As explained before, with the solenoid actua tor I44 de-energized, the torsion spring I22 will shift the swinging bracket I8 into position to bring the gears I I2 and 86 into engagement. This commences a timing cycle-which will determine the length of time that the toggle switch I32 will be closed. This switch is in series with the relay coil I66 and thus determines a period of energization for the said relay coil and therethrough of the stoker motor I10. Normally, this period of energization of the stoker motor is a matter of a few minutes every half hour or hour, depending upon the average outside temperature and the requirements of the building being heated, and, in general, is well known in the stoker art.

Normally, the reduced-fire cycling control will continue to operate unless the temperature of the building being warmed reaches a predetermined amount, at which time the thermostatic switch at I52 will close and will complete a circuit through the solenoid actuator I which will throw the reduced-fire cycling control into inoperative position, thus permitting the relay 0011 I66 and stoker motor I'II'I to remain de-energized until the building temperature is again reduced to permit the thermostatic switch-I52 to open.

Normally, the thermostatic switch I52 is set to open at a lower temperature than that at which the switch I62 will close, and preferably both of the thermostatic switches are adjustable according to well known practices.

After a' predetermined period of operation under the cycling reduced-fire control, the cam associated with the pointer and dial I8, 22, will again become effective to move the switch mechanism 68 into its Figure 9 position, and the stoker control will again operate on a normal daytime cycle. I

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

We claim:

1. In a stoker control; a stoker motor control relay, a thermostatic switch for controlling said relay during the normal firing operations, a reduced-fire control comprising a switch which closes at intervals tocontrol said relay, a second thermostatic switch for controlling said reducedfire control, and a time switch operable to make said first thermostatic switch and reduced-fire control alternatively effective for controlling said relay.

2. In a stoker control; a stoker motor control relay, a thermostatic switch for controlling said relay during the normal firing operations, a reduced-fire control comprising a switch which closes at intervals to control said relay, a second thermostatic switch for controlling said reducedfire control, a time switch operable to make said first thermostatic switch and reduced-fire control alternatively effective for controlling said relay, and a single synchronous electric motor connected to drive said time switch and said reduced-fire control.

3. In a stoker control; a stoker motor, a relay energizable to energize the stoker motor, a first thermostatic switch responsive to the temperature of the enclosure being heated for energizing said relay when the temperature falls below a predetermined amount and for de-energizing said relay when the temperature rises above a predetermined amount, a cycle switch connected with said relay operable for periodically energizing said relay for a predetermined length of time for reduced-fire operation of the stoker, a second thermostatic switch responsive to the temperature of the enclosure being heated for making said cycle switch ineffective for energizing said relay when the temperature rises above a predetermined amount and efiective for energizing said relay when said temperature falls below a predetermined amount, a two-position control switch connected in circuit with said thermostatic switches and having one position wherein one thermostatic switch is effective for controlling said relay and a second position wherein the other of the thermostatic switches is effective for controlling said cycle switch, and a synchronous motor and cam means driven by said motor for alternately actuating said two-position switch into its two operative positions so the said switch occupies one position for a part of a twenty-fourhour period and its other position for the remainder of the twenty-four-hour period, and said motor being operable to effect actuation of said cycle switch during the period of eifectiveness'of the cycle switch.

4. In a stoker control; a stoker motor, a relay energizable to energize the stoker motor, a first thermostatic switch responsive to the temperature of the enclosure being heated for energizing said relay when the temperature falls below a pre-" determined amount and for de-energizing said relay when the temperature rises above a predetermined amount, a cycle switch connected with said relay operable for periodically energizing said relay for a predetermined length of time for reduced-fire operation of the stoker, a second thermostatic switch responsive to the temperature of the enclosure being heated for making said cycle switch inefiective for energizing said relay when the temperature rises above a predetermined amount and effective for energizing said relay when said temperature falls below a predetermined amount, a two-position control switch connected in circuit with said thermostatic switches and having One position wherein one thermostatic switch is effective for controlling said relay and a second position wherein the other of the thermostatic switches is effective for controlling said cycle switch, and a synchro nous motor and cam means driven by said motor for alternately actuating said two position switch into its two operative positions and for actuating said cycle switch, said cam means being adjustable to predetermine the hours of the day said two-position switch will be in each of its two positions.

5. In a stoker control; a stoker motor, a relay energizable to energize the stoker motor, a first thermostatic switch responsive to the temperature of the enclosure being heated for energizing said relay when the temperature falls below a predetermined amount and for de-energizing said relay when the temperature rises above a predetermined amount, a cycle switch connected with said relay operable for periodically energizing said relay for a predetermined length of time for reduced-fire operation of the stoker, a second thermostatic switch responsive to the temperature of the enclosure being heated for making said cycle switch ineffective for energizing said relay when the temperature rises above a predetermined amount and effective for energizing said relay when said temperature falls below a predetermined amount, a two-position control switch connected in circuit with said thermostatic switches and having one position wherein said first switch is effective for controlling said relay and a second position wherein said second switch is effective for controlling said cycle switch, a synchronous motor, a cycle cam for said cycle switch geared to said motor, other cams connected with said motor for controlling said two-position switch, and electrical means controlled by said second thermostatic switch for disconnecting said cycle cam from said motor.

6. In a stoker control; a stoker motor, a control relay for said motor, a first thermostatic switch and a cycle switch in parallel and connected in series with said relay, a two-position switch having a first position wherein said thermostatic switch is efiective for controlling said relay and a second position wherein said cycle switch is effective for controlling said relay, electrical means energizable to make said cycle switch ineffective for controlling said relay, a second thermostatic switch for energizing said electrical means, and means responsive to movement of said two-position switch into its first position for energizing said electrical means.

7. In a stoker control; a stoker motor, a relay for controlling the energization of said motor, a first thermostatic switch and a cycle switch in parallel and connected in series with said relay, a two-position switch having a first position wherein said thermostatic switch is efiective for controlling said relay and a second position wherein said cycle switch is effective for controlling said relay, electrical means energizable to make said cycle switch ineffective for controlling said relay, a second thermostatic switch for energizing said electrical means, means responsive to movement of said two-position switch into its first position for energizing said electrical means, and a synchronous motor and cam means driven by said motor for controlling said two-position switch and said cycle switch.

8. In a stoker control; a stoker motor, a control relay for said motor, a first thermostatic switch and a cycle switch in parallel and connected in series with said relay, a two-position switch having a first position wherein said thermostatic switch is efiective for controlling said relay and a second position wherein said cycle switch is effective for controlling said relay, electrical means energizable to make said cycle switch ineifective for controlling said relay, a second thermostatic switch for energizing said electrical means, means responsive to movement of said two-position switch into its first position for energizing said electrical means, and a synchronous motor and cam means driven by said motor for controlling said two-position switch and said cycle switch, said cam means being adjustable for predetermining the periods of operation of said switches.

9. In a stoker control; a stoker motor, a control relay for said motor, a first thermostatic switch and a cycle switch in parallel and connected in series with said relay, a two-position switch having a first position wherein said thermostatic switch is efiective for controlling said relay and a second position wherein said cycle switch is effective for controlling said relay, electrical means energizable to make said cycle switch ineffective for controlling said relay, a second thermostatic switch for energizing said electrical means, means responsive to movement of said two-position switch into its first position for energizing said electrical means, a synchronous motor, first cam means connected with said motor for alternately moving said two-position switch into its two operative positions, second cam means connected with said motor for controlling said cycle switch, said electrical means being operative when energized for disconnecting said second cam means from said motor.

HARRY G. MANSON. ROBERT P. HANSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,720,723 Dodge July 16, 1929 1,885,963 Teeple Nov. 1, 1932 1,971,035 Fulton Aug. 21, 1934 2,057,309 Persons Oct. 13, 1936 2,268,711 Lewandowsky Jan. 6, 1942 2,342,211 Newton Feb. 22, 1944 

